This invention belongs to the field of organic chemistry and the synthesis of antibiotics. The invention provides a method for the removal of a carboxy-protecting group from cephalosporin, carbacephalosporin, penicillin and azetidin-2 one carboxylic acids using mild conditions. The carboxy group is desirably protected during the preparation of these compounds to block or prevent the otherwise reactive acidic carboxy group from participating in reactions that are in competition with a desired reaction at another site in the molecule. The esters are convenient and economical to handle in chemical processing but must eventually be removed because the compounds are used as antibiotics in either the acid or salt form. The ability to remove the carboxy-protecting group under mild conditions is useful because of the sensitivity of these .beta.-lactam compounds to heat, acidity and basicity.
The preparation of cephalosporins is taught broadly by Chauvette, U.S. Pat. No. 4,064,343. The preparation of 1-carbacephalosporins is taught broadly by Christensen, et al., in U.S. Pat. No. 4,226,866 and Munroe, in U.S. Pat. No. 4,791,106. The preparation of penicillins is taught by J. C. Sheehan and G. D. Laubach, (1951) J. Am. Chem. Soc., 73: 4376; J. C. Sheehan and E. J. Corey, (1951), J. Am. Chem. Soc., 73: 4756; J. C. Sheehan and G. D. Laubach, (1951), J. Am. Chem. Soc., 73: 4752. The preparation of azetidin-2-ones is taught broadly in Evans, et al. in U.S. Pat. No. 4,665,171.